Liquid level alarm



June 14, 1938. E. R. woLFERT 2,120,325

LIQUID LEVEL ALARM Filed April 6, 1935 2 Sheets-Sheet 1 FIG.!

I OEVAPORFITOR I5 CONDENSER Pic, 4, v WITNESSES: H 52 H H SIDE FLOAT VRLVE INVENTOR Epwnno E. won-sat ATTORN June 14, 1938. E. R. WOLFERT 2,120,325

LI UID LEVEL ALARM Filed April 6, 1935 2 Sheets-Sheet 2 THERHOSTRTIC EXPRNSION VHLVE 6B 71 es L FIG-6. I 57 THER MO STFIT l C VALVE INVENTOR m ATToRf Epwano E-WOLF'ERT;

Patented June 14, 1938 UNITED STATS PATENT OFFi LIQUID LEVEL ALARM Pennsylvania Application April 6, 1935, Serial No. 15,008.

13 Claims.

My invention relates to refrigerating apparatus, more particularly to apparatus for indicating leakage of refrigerant from the system, and it has for an object to provide improved apparatus.

In refrigerating apparatus having a liquid receiver and a thermostatic expansion valve or similar expansion device, a leakage indicating mechanism may be provided to give an alarm or other indication in response to drop in liquid level in the liquid receiver below a normal or predetermined level. When the refrigerating system is shut down, refrigerant may flow from the liquid receiver into another part of the system, for example, it may be absorbed by the oil in the compressor crank case. In such case, the consequent drop in liquid level is not a true indication of leakage of refrigerant from the system.

It is an object of my invention to avoid actuation of the leakage indicating mechanism when the drop in liquid level is due to flow of refrigerant into another part of the system rather than to leakage from the system.

In accordance with my invention, I provide means for initiating operation of the condensing unit in response to drop in liquid level,for the purpose of restoring the liquid level if the drop has been due to flow of refrigerant into another part of the system. The leakage indicating mechanism is arranged to function if the normal or predetermined level of liquid is not restored within a predetermined period of time thereafter.

The above and other objects are effected by my invention as will be apparent from the following description and claims taken in accordance with the accompanying drawings forming a part of this application, in which:

Fig. l is a diagrammatic view of a refrigerating system embodying one form of my invention;

Fig. 2 is a plan view of the liquid level responsive mechanism;

Fig. 3 is an elevation of a modified form of liquid level responsive mechanism;

Fig. 4 is a diagrammatic view of a modified portion of the refrigerating system; and,

Figs. 5, 6, and 7 show diagrammatically three embodiments of the invention in which provision is made for the variations in liquid level due to operating conditions and not to leakage.

' Referring to the drawings in detail, I show a refrigerating system of known construction. including a compressor l operated by amotor ii, a condenser H, a liquid receiver or reservoir is, a thermostatic expansion valve M, and an evaporator I5, said elements of the system being connected for flow of refrigerant therethrough in the order named and from the evaporator to the compressor. The thermostatic expansion 'valve M is of conventional construction, including a diaphragm i6 subjected on its lower side to the pressure in the evaporator l and to the force of a compression spring 20. It further includes a thermostatic bulb H, which develops a pressure varying as a function of the temperature of the discharged vapor in the suction conduit I8. This pressure is conveyed through a tube l9 and imposed .on the upper side of the diaphragm I6 in valve closing direction. The valve 84 thus operates to admit such quantity of liquid to the evaporator as can be fully vaporized therein and superheated to a predetermined degree, as is well known in the art.

If refrigerant should leak out of the system at any time, the quantity of liquid contained in the reservoir i3 is reduced, while the thermostatic expansion valve it continues to withdraw liquid refrigerant therefrom to supply the evaporator It. In accordance with my invention, I provide a mechanismwhich responds to the liquid level in the reservoir i3, whereby leakage from the re-f frigerating system can be determined.

The liquid level responsive mechanism of Fig. 1 is of novel construction and includes a magnetic circuit extending through an end wall 2i of the liquidreceiver, which end wall is made of a nonmagnetic material, such as' brass. The mag-. netic circuit comprises two members 22 of soift iron or other material which may be magnetized but which does not retain the magnetism when the source of magnetism is removed. These nonretentive magnetizable members 22 extend through openings in the brass wall it, said openings being preferably closed and sealed by silver solder. An armature 23 carried on a lever 2| pivoted at 25, bridges theouter ends or the The lever 25 actuated by the armature 23 is I adapted to move an electrical contact 32 intoengagement with a stationary contact 33. The contacts 32 and 33 are connected in an electrical circuit it, which may be used either to operate a warning device or to shut down the refrigerating system by deenergizing the motor H, or both. The solenoid of a relay is connected in the circuit 34, the contacts of the relay being connected in the circuit 33 for the motor ll. Also, a warning device, such as a bell 31, is connected in the circuit in parallel with the relay 33. Switches 38 and 39 are provided for the bell 31 and the relay 35, respectively, so that either or both of such devices may be rendered operative or inoperative at will. The circuit 36 is provided with any suitable control mechanism known in the art, a simple two-pole switch being illuspressure thereof being reduced by the thermostatic expansion valve |4. The liquid refrigerant is evaporated in the evaporator and the vaporized refrigerant is returned to the compressor again to be compressed. As refrigerant leaks out of the system, the supply of liquid refrigerant in the liquid receiver I3 is drawn upon, causingthe liquid level to be lowered.

The operation of the liquid level responsive mechanism is as follows: As the liquid level in the receiver l3 drops, the float member 3| moves the permanent magnet 21, through the lever 28, toward the members 22, and as the liquid level rises, the float member moves the permanent magnet away from the members 23. As the liquid level reaches such a' low point as to indicate that refrigerant is leaking from the system, the permanent magnet 21 is moved so close to the members 22 as to magnetize theomagnet I plenished, the float member 3| rises in response to a higher or normal liquid level and moves the permanent magnet 21 away from the member 22. Thermagnetic circuit is thereupon deenergized and the spring 23 moves the lever 24 to open the contacts 32 and 33. The circuit 34 is thereupon opened.

The provision of a permanent magnet as the movable member for controlling the magnetization of the magnet circuit provides a deflnite pull-in point, that is, the point at which the contacts close is very definite; therefore the device is quite accurate in operation. Also, the provision of a permanent magnet avoids the ne-'- cessity of a regulated source of voltage and a constant source of energy.

that, .as the glass bulb is ti1ted by downward movement of the float member 3|, the mercury closes the circuit between the two contacts, while, if it is tilted in the opposite direction, the circuit is opened. The contacts are ,connected by flexible leads 43 and 44, and by studs 43 and 43 extending through the wall of the reservoir to the circuit 34 of Fig. 1, said contacts thereby effecting the same function as the contacts 32 and 33 of Fig. 1. r

In the operation of this mechanism, as the liquid level drops to a predetermined point, .the float member 3| tilts the switch." in clockwise direction to close the circuit 23 through the contacts of the switch 42. As the quantity of liquid refrigerant is replenished to raise the liquid level, the float member 3| tilts the switch 42 in counterclockwise direction to open the circuit.

In the refrigerating apparatus of Fig. 4, a high side float valve 3 lcontrols the flow of liquid refrigerant from-the high side to the low side and reduces the pressure thereof. It is connected through a conduit ,32 to the header 33 of a flooded evaporator 34. In this case, the float valve admits all the condensed refrigerant conveyed to it, except a small substantially constant quantity required for operation of the float therein, so that the variation in quantity of refrigerant in the system is effected in the header 53. Accordingly, in this case, I provide a liquid level responsive mechanism 53, such as that shown in Fig. 3, within the header 53 so as to respond to the liquid level therein. The operation of this embodiment is the same as that of the embodiment shown in Fig. 3. I

I have foiind that, when refrigeratingapparatus using a refrigerant soluble in oil lsnot rection by. solenoids 31.

nected to the circuit 33 in parallel with the comoperated for long periods, some of the refrigerant passes from the liquid receiver or other part of the high side, usually due to absorption of refrigerant vapor by the oil in the crank case. In such case, a drop in liquid level will give a false indication since there has been no actual loss of refrigerant from the system. To overcomethis difliculty, one of the schemes shown in'Figs. 5 to 7 may be used. 1

In the apparatus of Fig. 5, I use a watercooled condenser 33 comprising a chamber 31 in which a water cooling coil 33 is disposed. The bottom of the chamber 31 serves as the liquid receiver. The liquid level responsive mechanism is contained in a chamber 33 which is connected to the chamber 31 by a pipe 3| of large diameter so positioned that the liquid level is always between the top and bottom of the interior of the pipe whereby the liquid level in the chambers 37 and 33 is always the same. ment, I provide a valve 32 in the conduit 33 connecting the discharge of the compressor II to the condenser, and a valve 34 in the conduit 33 connecting thecondenser tothe evaporator. The valves 32 and 34 are biased to closed position by springs 33 and are actuated in open di- The latter are conpressor motor In Fig. '3, I show a modified form of liquid level responsive mechanism in which a mercury switch 42 mounted on the lever .23 to which the float member'3l is attached. The switch 42 comprises a glass bulb containing a small quantity of mercury and two contacts arranged in such position In the operation of this embodiment, the solenoids 31 are energized by the circuit 33 simultaneously'with the compressor motor II to pert flow of refrigerant through the conduits 33 a d 33 for operation of the refrigerating apparatus. When the circuit 33 is opened to discontinue refrigerating operation, the solenoids are de-energized and the'springs 33 close'the valves 32 and 34. Escape of refrigerant from the cham- In this embodiher 51 and consequent drop in liquid level is thus through a circuit 8lextending from the line prevented. The, liquid level responsive mechaconductor L1, through the winding of the relay nism thus responds only to a decrease to liquid 13, the contacts 19, and then joining the circuit level indicating leakage of refrigerant from the 15 to continue through the contacts 11' to the apparatus and may either effect an alarm or open line conductor L2. The time delay device 18 the circuit 36, or preferably do both, as previously comprises an electrical resistance heating eledescribed. ment 82 connected in a circuit 83 extending from Referring to Fig. 6, leakage of refrigerant to the line conductor Ll, through one pole of a manthe low side of the system causes an increase in ually actuated switch 86, contacts 85 of the relay pressure therein, so that if the compressor is '16, and the heating element 82 to the line con- 10 operated in response to such increased pressure, ductor L2. .The time delay device 18 further inthe escaped refrigerant will be returned to the cludes a temperature responsive element 86, chamber 51 before sufficient refrigerant has which is subjected to the heat generated by the leaked out to give a false alarm. A pressureheating element .82, and which is adapted to responsive device 68 is connected by a conduit open the contacts 11 and to close another set of 69 to the suction conduit ll connecting the outlet contacts 81, when the heating element has been of the evaporator with the inlet of the comenergized for apredetermined-period of time. pressor, and operates a switch 12 controlling a The contacts 81 are adapted to close an alarm relay 13 that is adapted to open the compressor circuit 88 for energizing an alarm device 89. motor circuit 36. A thermostat T, responsive to The circuit 88 also extends through a second pole the cooling load, actuates a valve 14 controlling of the manually actuated switch 84,- and it is supply of liquid refrigerant to the evaporator. energized by a transformer 90, the primary wind- In the operation of the apparatus of Fig 6, the ing of which is connected across the line condevice 68 operates in response to a predetermined ductors L1 and L2. maximum pressure in the low side, such as 65 to The operation of the embodiment shown in '70 lbs. per sq. in. when using Freon, to close Fig. l is as follows: As the liquid level inthe conthe switch 12 thereby actuating relay I3 to close denser 56 drops to a predetermined point, the the compressor motor circuit 36. switch in the chamber 59 closes the circuit 15, The compressor operates until the pressure in whereupon the energized relay l6 .closes its con; the low side is reduced to a predetermined minitacts 19 and 85. The contacts I9 complete the mum such as 25 lbs. per sq. in. When the thercircuit 8|, so that the relay l3 startsthe motor mostat admits liquid refrigerant to the evapoand compressor. Any refrigerant which may rator to supply the cooling load, the evaporation have escaped to the low side of the system, is reof refrigerant in the evaporator raises thepresturned to the condenser. The contacts 85 close sure so that operation of the apparatus is efthe circuit 83 to energize the heating element 82. fected as just described. If the thermostat does If the normal liquid level is restored, by return not operate to open the valve 14 for a long period of refrigerant to the condenser, before the heatof time, leakage of refrigerant raises the pre ing element 82 has been heated to a temperature sure in the low side, so that the compressor is causing the thermostatic element 86 to Operate,

. operated as described to return the refrigerant to the switch in the chamber 59 reopens the circuit 40 thechamber 51. Thus, the liquid level responsive l5 te deenergize the relay 16. Further operation mechanism in the chamber 51 operates in the o hem or and mp sor, so fa as i m be same manner as in the previous embodiments, effected by the liquid level respo sive mechanism, and only to indicate leakage of refrigerant. is terminated: t y. hOWBVeI. be continued A particular advantage of the valve M in this by the thermostat 9! which normally controls the arrangement is that it permits operation f the operation. The contacts 85 discontinue further compressor toreturn escaped refrigerant to the t g of the element 82. Thus, when the drop chamber 51 without effecting refrigeration in the i iq id l v l i e o e ap f r fr to evaporator when such refrigeration is n t dethe low side, the refrigerant is returned tothe sired. Suppose, for example, that sufll i m; recondenser and sounding of the alarm is avoided.

frlgerant has escaped int the low pressure d If the normal liquid level is not restored within to causethe pressure responsive device 68 to a predetermined p d Of time, the heating effect operation of the compressor but that the m 52 reaches a tempe ature causing the temcooling load is light and refrigeration is not deperatllle responsive element 36 110 p the (50!!- sired. The valve H cuts off the fiow of liquid tacts 11 and close the contacts 81, the element 55 refrigerant to the evaporator while the compres- 86 being ed in Su Position b a latching sor is operating, whereby such undesired refrigmechanism 9 Th opening of h a ts 11 eration is void d, opens the circuits l5 and 8|, so that further op- In Fig.7, I show the preferred mb di t of eration of the compressor and motor under conmy invention. when the liquid 1 v 1 drops t a trol of the liquid level responsive mechanism is predetermined low point, the compressor is first terminetcde closing of t e cont cts 8 comoperated to return to the condenser or liquid P the circuit 33, u e devlce 39 0 reservoir refrigerant that has escaped to the low sound an alarm, indicating t at l qu d r ant side before sounding an alarm. The apparatus escaped from the systemp h ar ng t includes a water cooled condenser 56 connected alarm, theopelator may Open the SwitQh 34 to by a pipe 6| to a chamber 59, as in Figs, 5 and discontinue furthersounding of the alarm. The The chamber. 9 f bl m a fl at refrigerating capacityof the mechanism remains switch 42 as shown in Fig. 3. available, however, under control of the normal The switch in the chamber 59 is connect-ed in thermostat a circuit 15; the latter extending from line con- W the trouble has been Corrected anfkthe ductor Ll through the winding of a relay 16, t normal liquid level restored, the time delay device switch in the chamber 59, and the normally 1B is unlatched and the manual switch 8 8 roclosed'contacts 11 of atime delay device 18, to closed to render the mechanism again operable the line conductor L2. The relay 16 has one for sounding an alarm. set of contacts 19 for controlling the relay 13 From the above description, it W111 be seen that I have provided apparatus which will sound an alarm or give a signal when a predetermined quantity of refrigerant, for example, 10 pounds, has escaped from the system.

While I have shown 'my invention in several forms, it will be obvious to those skilled in the art that it is not-so limited, but is susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. In a refrigerating system, the combination of a compressor, a motor for driving the compressor, a condenser, a liquid receiver, an evaporator, a magnetic circuit extending through a wall portion of the liquid receiver and including an armature located exteriorly of the liquid receiver and a magnet located interiorly thereof. a warning signal or alarm, a circuit for said warning signal or alarm controlled by said armature, and means responsive to a predetermined low-liquid level in the liquid receiver for actuating said magnet so as to magnetize said magnetic circuit and operate said armature to effect operation of said warning signal or alarm.

2. In a refrigerating system the combination of a compressor, a motor for driving the compressor, a condenser, a liquid receiver, an evaporator, a magnetic circuit extending through a wall portion of the liquid receiver and including an armature located exteriorly of the liquid receiver, a, float member within the liquid receiver and operable to close and open said magnetic circuit upon variation in liquid level within the liquid receiver, and means responsive to operation of said armature for deenergizing said motor, said parts being so arranged that said motor is deenergized when a predetermined low liquid level in the liquid receiver is reached.

3. The combination with a refrigerating system including means for liquefying vaporized re-. frigerant and circulating refrigerant through the system and including a reservoir for liquid refrigerant in which the liquid level-is affected by the quantity of refrigerant in the system, of a device to be operated when the quantity of refrigerant in the system'has decreased to a value indicating leakage of refrigerant from' the system, a time-delay device, means responsive to a predetermined low liquid level in saidreservoir for effecting operation of said liquefying and circulating means and of-said time delay device and I responsive to a higher or normal liquid level for terminating its action in effecting operation of said liquefying and circulating means andforterminating operation of said time relay device, and means controlled by the time-delay device when operated for a predetermined period of time for effecting operation of said first-mentioned de- I vice.

4. The combination with a refrigerating system including means for liquefying vaporized refrigerant and circulating refrigerant through the system and including a reservoir forliquid refrigerant in which the liquid level is affected by'the quantity of refrigerant in the system, of an indicating device to be operated when the quantity of refrigerant in the system has decreasedto a value indicating leakage of refrigerant from the system,'means responsive to decrease in liquid level in said reservoir below a Z normal level foreffecting operation of said circulating means and for operating said indicating device if the normal liquid level is not restored within a predetermined period of time.

5. The combination with a refrigerating system including a compressor and a reservoir for liquid refrigerant in which the liquid level is affected by the quantity of refrigerant in the system, of a warning device to be operated when the quantity of refrigerant in the system has decreased to a value indicating leakage of refrigerant from the system, a time delay device, means for automatically controlling the operation of the compressor in accordance. with the refrigerating demand, means responsive to a predetermined low liquid level in said reservoir for effecting operation of said compressor independently of the action of said first mentioned means and operation of said time delay device and responsive to a higher or normal liquid level for terminating its action in eifecting operation of said compressor and for terminating operation of said time delay device, and means controlled by the time delay device when operated for a predetermined period of time for effecting ant therein in normal operation, a portion of which is liquid and a portion of which is vapor, the combination of means for condensing vaporous refrigerant, a container for liquid refrigerant, means responsive to a deficiency in tlie quantity of liquid refrigerant in the container for initiating operation of the condensing means and for continuing operation thereof within a predetermined period of time thereafter as long as the deficiency exists, a leakage indicating device, and means for effecting operation of the leakage indicating device in response to a deflciency of liquid refrigerant in said container at the end of said predetermined period of time.

'7. The combination with a refrigerating system including a compressor and a reservoir for liquid refrigerant in which the liquid level is affected by the quantity of refrigerant in the system, of means dependent upon both operation of the compressor for a predetermined period of time and a predetermined low liquid level at the end of said predetermined period of time, to give a warning.

8. The combination with a refrigerating system including a compressor and a reservoir for liquid refrigerant in which the liquid level is affected by the quantity of refrigerant in the system, of means responsive to a predetermined low liquid level in the reservoir for effecting operation of the compressor, and means dependent upon both operation of the compressor for a predetermined period of time and a predetermined low liquid level at the end of said predetermined period oftime, to give a warning.

9. The method of controlling the operation of a warning device for indicating leakage of re-.

frigerant from a refrigerating system including a. compressor and a reservoir for liquid refrigerant, which method comprises operating the compressor inresponse to a predetermined low -liquid level in said reservoir and efiecting operation of said warning device in response to continuance of a predetermined low liquid level for a predetermined period of time.

11. The combination'with a refrigerating system including an evaporator, a compressor and a condenser, said refrigerating system including. a reservoir for liquid refrigerant in which the liquid level is effected by the quantity of refrigerant in the system, a warning device, means responsive to a predetermined low liquid level in said reservoir for effecting operation of said warning device, and means for preventing operation of said warning device in response to a low liquid level if the drop in said liquid level is due to a cause other than leakage of refrigerant from the system.

1 12. The combination with a refrigerating sys-' tem including an evaporator, a compressor having a crankcase connected in the low pressure side of the system and adapted to contain oil for, lubrication of the compressor, and a condenser,

said refrigerating system includinga reservoir for liquid refrigerant connected in the high pressure side of the system and inwhich the liquid level is affected by the quantity of refrigerant in the system, of a valve for controlling the flow of liquid refrigerant from said high pressure side to said evaporator, a thermostat responsive to the cooling load of the apparatus for controlling said valve, means for effecting operation of said compressor in-response to an operating condition of the. refrigerating system that may be caused by leakage of refrigerant from the high pressure side to the low side of the system, whereby excessive refrigerant absorbed by the oil-in sure side of the system and in which the liquid 1 level is affected by the quantity of refrigerant in the system, of a valve for controlling the flow, of

liquid refrigerant from said high pressure side to said evaporator, a thermostat responsive to the cooling load of the apparatus for controlling said pressor in response to a predetermined maximum pressure of the refrigerant in the low pressure side of the system, whereby excessive refrigerant absorbed by the oil in the crankcase of the compressor is withdrawn therefrom and returned to the reservoir to restore'the liquid level therein, a

warning device, and means responsive to a preefiecting operation of said warning device.

EDWARD R. WOLFERT.

valve, 'means for effecting operation of said comso determined low liquid level. in said reservoir for i 

